This invention generally relates to formulations of paclitaxel and more particularly to methods of making formulations of paclitaxel.
Paclitaxel is a natural product which has been shown to possess cytotoxic and antitumor activity. Indeed, paclitaxel may be among the most active single agent for ovarian and breast cancers. This compound is found in small concentrations in the Taxus brevifolia species such as the Pacific yew tree among other Taxus species. While having an unambiguous reputation of tremendous therapeutic potential, paclitaxel as a therapeutic agent has some patient related drawbacks. These stem, in part, from its extremely low solubility in water, which makes it difficult to provide in suitable dosage form. Because of paclitaxel""s poor aqueous solubility, the current approved clinical formulation consists of a 6 mg/ml solution of paclitaxel in 50% polyoxyethylated castor oil (CREMOPHOR EL(trademark)) and 50% dehydrated alcohol. Am. J. Hosp. Pharm., 48:1520-24 (1991). In some instances, severe reactions, including hypersensitivity, occur in conjunction with the CREMOPHOR(trademark) administered in conjunction with paclitaxel to compensate for its low water solubility. As a result of the incidence of hypersensitivity reactions to the commercial paclitaxel formulations and the potential for paclitaxel precipitation in the blood, the formulation must be infused over several hours. In addition, patients must be pretreated with steroids and antihistamines prior to the infusion.
In response to the hypersensitivity related to the CREMOPHOR(trademark), the increasing recognition of paclitaxel""s promise as an antineoplastic, and the undesirability of having to infuse the paclitaxel over several hours, there remains a need to develop improved formulations of the paclitaxel which can be administered as bolus injections.
It is therefore an object of the present invention to provide compositions of the paclitaxel without the solubilizing agent, CREMOPHOR(trademark) which is present in the commercial formulation.
It is another object of the present invention to provide methods for producing the porous dry powder formulations of paclitaxel or docetaxol.
It is another object of the present invention to provide compositions providing enhanced dissolution of paclitaxel or docetaxol in a formulation suitable for administration by a variety of routes, including, but not limited to, parenteral, mucosal, oral, and topical administration, for local, regional, or systemic effect.
It is further object of the present invention to provide paclitaxel compositions for administration as a bolus injection instead of by infusion.
Paclitaxel is provided in a porous matrix form which forms nanoparticles and microparticles of paclitaxel when the matrix is contacted with an aqueous medium. The porous matrix with paclitaxel yields upon contact with an aqueous medium microparticles having a mean diameter between about 0.01 and 5 xcexcm and a total surface area greater than about 0.5 m2/mL. The dry porous matrix is in a dry powder form having a TAP density less than or equal to 1.0 g/mL.
The porous matrices that contain the paclitaxel are preferably made using a process that includes (i) dissolving a paclitaxel in a volatile solvent to form a paclitaxel solution, (ii) combining at least one pore forming agent with the paclitaxel solution to form an emulsion, suspension, or second solution, and (iii) removing the volatile solvent and pore forming agent from the emulsion, suspension, or second solution to yield the dry porous matrix of paclitaxel. The resulting porous matrix has a faster rate of dissolution following administration to a patient, as compared to non-porous matrix forms of the paclitaxel. The pore forming agent can be either a volatile liquid that is immiscible with the paclitaxel solvent or a volatile solid compound, preferably a volatile salt. If the pore forming agent is a liquid, the agent is emulsified with the paclitaxel solution. If the pore forming agent is a solid, the agent is (i) dissolved in the paclitaxel solution, (ii) dissolved in a solvent that is not miscible in the paclitaxel solvent and then emulsified with the paclitaxel solution, or (iii) suspended as solid particulates in the paclitaxel solution. Optionally, hydrophilic excipients, wetting agents, and/or tonicity agents may be added to the paclitaxel solvent, the pore forming agent solvent, or both. The solution, emulsion, or suspension of the pore forming agent in the paclitaxel solution is then processed to remove the paclitaxel solvent and the pore forming agent, as well as any pore forming agent solvent. In a preferred embodiment, spray drying, optionally followed by lyophilization, fluid bed drying, or vacuum drying, is used to remove the solvents and the pore forming agent.
An advantage of the formulations is that they can be administered as a bolus, when the paclitaxel normally must be infused to avoid toxicity and to avoid precipitation of the drug. By avoiding precipitation of paclitaxel in vivo, the formulations can also be administered intrarterially, intravenously, locally, intracranially, intrathecally, or directly into a tumor. An additional advantage is the formulations can be administered in reduced volumes.
In one embodiment, the matrix further includes a pegylated excipient with the paclitaxel. The pegylated excipient shields the paclitaxel from macrophage uptake, which prolong its half-life or enhance bioavailability of the paclitaxel.
In a preferred embodiment, the porous paclitaxel matrix is reconstituted with an aqueous medium and administered parenterally, such as intramuscularly, subcutaneously, or intravenously. Alternatively, the porous paclitaxel matrix can be further processed using standard techniques into tablets or capsules for oral administration or into rectal suppositories, delivered using a dry powder inhaler for pulmonary administration, or mixed/processed into a cream or ointment for topical administration.